It is clear that factors governing enzyme catalysis originate in the various intermediates of the mechanism. Therefore, any study of these factors must begin with a full characterization of intermediates in terms of delta G, delta H, delta S, delta G activated complex, delta H activated complex, delta S activated complex. This research is designed to obtain thermodynamic data on alpha-chymotrypsin catalyzed hydrolysis of esters and imides which uniquely form stable covalent acyl enzyme intermediates. The goal is to use this kind of data to seek quantitative information on some features of enzyme action believed to be important in catalysis. Microcalorimetry will be extensively used to obtain not only enthalpy changes of intermediates but also to derive estimates of thermodynamic changes for such factors as (1) "conformation" differences between acyl enzyme and the acid enzyme complex (deacylation product), (2) bond rearrangement and bond breaking occurring within the enzyme intermediate, and (3) the role of strain as a component of the substrate and subsequently the acyl enzyme itself. The objective is to develop new techniques for quantitative study of these elusive aspects of catalysis. Kinetic evaluation of delta G activated complex, delta H activated complex, and delta S activated complex will give information on the dynamics of the intermediates and thus, in combination with the equilibrium thermodynamic data, provide a foundation for continued investigation of problems on the nature of catalysis.